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03 July 2015

A healthy ocean is essential for a healthy planet, and ultimately our own survival.  Yet the life-giving seas are under serious threat. Now a group of leading marine scientists are calling on policy makers to heed their warnings to ensure that the ocean and its future sustainability are given the attention they scientifically deserve at forthcoming climate negotiations.

The world ocean covers around three quarters of the Earth; it provides food, energy, minerals, drugs and it regulates climate and weather. Even in the face of climate change the ocean has absorbed over 90% of the additional heat created by human activities since 1970 and thus reducing the impacts of climate change in the atmosphere and on land. Nearly 30% of the carbon dioxide produced since 1750 from industry and the use of fossil fuels has been absorbed by the ocean. The ocean also accumulates virtually all water resulting from melting glaciers and ice sheets. But all of this has come at a price: the ocean is warming, and sea levels are rising – and while the ocean is a natural sink for CO2, the increased rate of uptake is changing the very chemistry of seawater, causing ocean acidification as pH falls. All these impacts of human activities are now being seen in what was once thought to be a vast untouchable ocean.

Now, twenty-two of the world’s leading marine scientists including British scientists from Plymouth Marine Laboratory, the University of Oxford and Scottish Natural Heritage, are asking policy makers to recognise the potential consequences of these dramatic changes that are taking place in the ocean and to raise the profile of the ocean in international talks.  In an article published today in the highly respected journal Science, the group of specialists bring together, for the first time, a summary of expected impacts of ocean acidification, warming and deoxygenation, impacting singly and together on some of the key goods and services upon which we rely. They also call for a higher profile for the ocean in future climate change talks: Jean-Pierre Gattuso of the Villefranche Oceanography Laboratory and  lead author of the study said, “the ocean has been minimally considered at previous climate negotiations; our study provides compelling arguments for a radical change at COP21, the United Nations conference on climate change”.

Using two of the projected scenarios for future carbon dioxide emissions until 2100, the scientists conclude that under a low mitigation, high emissions scenario biological ocean impacts, and their social consequences, would be considerably higher than if there is a strong climate agreement, with low emissions. The low emissions scenario is however that would also involve risks of significant ocean impacts.

Co-author Dr Carol Turley of Plymouth Marine Laboratory and the UK Ocean Acidification research programme (UKOA), said “The ocean is at the frontline of climate change with its physics and chemistry being altered at an unprecedented rate so much so that ecosystems and organisms are already changing and will continue to do so as we emit more carbon dioxide to the atmosphere.”

Species are changing where they live in the ocean as temperatures rise, whilst ocean acidification is likely to impact on reproduction, larval survival and feeding, and growth rates of marine organisms, especially those that have calcium carbonate shells or skeletons. Deoxygenation, largely due to coastal pollution and increased stratification caused by warming, adds another stressor to an already delicate ocean balance, creating large areas of sea bed that are effectively dead to all but bacteria. When the three stressors occur together they occasionally cancel each other out, but also often serve to multiply negative effects. Coastal protection, fisheries, aquaculture and human health and tourism will all be affected.

Impacts have already been identified, and are expected to worsen from the equator to the poles, and are thus a global concern. As a result, “given the extent of the expected changes, no country is in a safe position, making this issue a worldwide problem that challenges the traditional North/South divide”, said Alexandre Magnan, of the Institute for Sustainable Development and International Relations, and co-author of the paper. The scientists further state in their article that “immediate and substantial reduction of CO2 emissions is required in order to prevent the massive and effectively irreversible impacts on ocean ecosystems and their services”. The overwhelming conclusion from their assessment is clear: the options for repair, adaption and protection become fewer and less effective for the ocean as CO2 increases.